Useful industrial multi-phase processes frequently depend upon effective access of a consumable gaseous resource to an active liquid phase. In complex systems such, for example as a microorganismic culture medium, which is frequently an aqueous soup or broth, a third phase can be present which interferes with the mass transfer of such gaseous or vaporous resource across a gas-liquid interface. A typical undesired third phase is a hydrophobic slick or slime, rich in oils, greases or fats, which can coat the interface smothering and interfering with mass transfer.
Cultivation of microorganisms, or microorganisms, in tanks or vats, pipes and other process equipment is an important industrial activity responsible for the production inter alia of food supplements and pharmaceuticals. Industrial microbiological processes are carefully managed as to conditions of temperature, nutrient stock and residence time in order to optimize efficiency. Other precautions are commonly taken to prevent ingress of foreign organisms which might flourish in the nutrient-rich process broths employed, seriously contaminating them. In other words, the environment around the tanks is generally kept aseptic or sterile. Precise characterization and control of the process microorganisms is the norm in a well-developed and fastidious industry.
The present invention is particularly concerned with processes employing aerobic microorganisms, i.e. microorganisms, including bacteria and useful fungi such as yeasts, whose metabolic processes require the presence of oxygen, and are cultured in substantially aqueous growth media. Many such cultivation processes generate oily or greasy residues which rise to the surface of the process vessel and form a gas-transport inhibitive impermeable hydrophobic third phase in the form of a slick or film at the air-liquid interface. This hydrophobic third phase is a substantial barrier to oxygen access, inhibits microorganismic activity and greatly reduces process efficiency.
To improve aeration, and thence oxygen access to aerobic culture media, many and various agitation devices are customarily used. However, they do not destroy the hydrophobic third phase, so that aeration efficiency is still impaired. Mechanical removal of this hydrophobic third phase, for example by skimming, may reduce the third phase but is not effective in eliminating the smothering effect of the third phase. Also, skimming is difficult to execute effectively, especially in a vigorously agitated vessel, and wastes culture medium. Such mechanical treatments leave a hydrophobic residue to impede gas transport at the interface.
Because of his background and experience the present inventor is familiar with commercial processes involving major microfloral growths in the alien environment of sewage treatment.
The "Griffin Oxinite Process", Griffin Pollution Control Corporation, Yonkers, N. Y., (1970) discloses a process for the gaseous treatment of sewage with activated air, which is effective in reducing odor, crown corrosion and slime build up on superstructures. The activated air used in the "Oxinite" ("Oxinite" is a trademark of Griffin Pollution Control Corporation) process is prepared by subjecting air to electrical discharge and de-ozonization. Further benefits of the "Oxinite" process include humidity reductions, accelerated bacterial growth, grease reduction and the increase of dissolved oxygen in both gravity-fed and pumped sewage systems.
Kellum U.S. Pat. No. 3,344,061, assigned to Griffin Pollution Control Corporation, discloses a sewage treatment process similar to the "Oxinite" process and using de-ozonized activated air, which asserts the benefits of reduced biological demand, elimination of noxious odors and reduction of sulfide formation as well as reduction of dangerous methane generation.
Beyond harboring microorganisms, there is little to connect the fields of sewage treatment and the industrial culture of microorganisms. The one is a highly technical, controlled process employing specific or narrow-band worker microorganisms and conducted under conditions that accurately maintain preferred temperature and pH ranges and exclude ingress of undesired organisms that could rapidly multiply in the process soup, whereas the other is a low technology imprecise field rife with organisms of every description. The physical dispersion of the multi-phase constituents is also different including, in the case of sewage heterogenous solid-liquid mixtures and an interactive overhead environment.
Skilled workers in the art of industrial microbiology are not likely to perceive useful teachings to be obtainable from the art of sewage treatment: the arts are not analogous.
Other microrganismic processes to which the invention is applicable include processes employing anerobic organisms requiring a gaseous resource such as carbon dioxide, ammonia, methane or hydrogen sulfide. Worker microorganisms have utility not just for synthesis processes which yield a useful product such as a foodstuff or pharmaceutical, but also in digestive processes which breakdown undesired complex materials, such as sewage or cellulose into simpler, more readily disposable products.
In general, the invention is applicable to processes where the worker microorganisms are maintained in or dependent on a substantially aqueous phase.